Drill bit



Nov. 1l, 1941. M. HoKANsoN DRILL BIT Filed Aug. 21, 1939 2 Sheets-Sheetl ATTRNEY.

Nov. l1, 1941A. M. HoKANsoN DRILL BIT 2 Sheets-Sheet 2 1N ENTOR, 6ATT'ORNEY.

PatentedA Nov.` 11, 1941 Meran noknnson, Duluth.' Minn., assigner teEidco, Incorporated, Duluth, Minn., a corporation of Minnesota'-nppueeuen August ai, 1939, serial No.- 291,168

This invention relates te drl special reference to improveme ts in thattype of bit illustrated in my United States Patent No.

2,147,343, dated Feb. 14, 1939, and in my cOpeIld-V ing applications,Ser. Numbers 251,830; 264,791 and 284,939, and is indicative of that'type -of shown as being screw-threaded as by V-shaped improvements thatcan only be accomplished by.l l

continued and extensive experimentation in' actual practice with such adrill.

It has been found that in the larger types oi such a drill, increasedspeed and emciency are accomplished by the material modications andimprovements shown, described` and claimed in' the instant case.

The duplication of the reaming action of an intermediate cutting portionof the bit is believed very material in the practical use ofmthe 'e bitin respect to both speed of cutting. and

This is particularly true l straightness of hole. e when it is realizedthat in a large bit of this type, the intermediate reamerI protrudesmaterially beyond the plane of the cutting edge of the cuter-y or majorreamer, but, due to its relatively short length, requires no clearancetaper whatever,

which reduces the gage loss to an absolute minimum, and also has theminimum tendency deviation from a straight hole,

A further advantage of duplication ofy the major reaming portion is thatthey diier only'fin. j

size and are subj ect to repeated sharpening from the inside of thedepression by a likeshaped grinding or forming tool.

The principal object of the invention is, to divide up the ring formedbetween the outside reamer and the centralcutter by means of one or moresub-reamers. In this waythe width of these rings are cut in half or athird, etc.,

which makes the spalls less in size and more suitable for discharge outof the hole. f Other objects and advantages of the inven-f tion willappear in the following description Referring now to the accompanying`drawings, forming part of this application, and wherein like.

reference characters indicate like parts:

Figure 1 is a central vertical section, partly in volume. forgets-7a)bits and` has and 2 the various `cooperative parts of the bit arethreading of the parts, it is thought obvious that in view of thevarious forms of such union as for example by square threads, ormodiiied fric-y tion joints, which may be resorted to and are common inthe art, further illustration or reference thereto is unnecessary, orthat the parts may beformedintegral as shownl in Fig. 4, or 10,

any one of them separable as shown in Figure 5, without departing fromthe spirit of the invention.A v v y Inall. modifications I have,illustrated the bit as' beingprovidd with' a tapered yspigot `I for asuitable friction union to the operating mecha- `nism for impartingreciprocal motion thereto, and this may be either a drill rod or a cableoperating means I'he spigot Itis shown as being formed integral with thecylindrical shank 2 of the bit, which, in this instance, tapers from thelower portion thereof in opposite directions, as at 3, to the uppersmaller end of the headrportion 4. This Vhead portion is illustrated ascomprising two opposed arcuate vrearning portionsS lying in the samecircle with the diametrcally opposite portions of the head being attenedas illustrated at 6 in p planes parallel with the axis and extendingupwardly from the corners of the reaming edges to the point indicated at1, which point is the junction of the inclined surface 3 with such planesurfaces. j j y l The attening of the sides in this manner is to provideample clearance for the detritus or spalls, and obviously maybe enlargedor reduced as required in 'respect to the character of the materialbeing drilled.' However the proportions here illustrated'are `deemedideal in that such ample clearance is provided, and the strength of thebit head is in no wise impaired.

To further insure ample clearance for spalls it is to be noted that thelower edge of the head elevation, of a drill bit embodying theinvention. y

Figure 2 is a similar view taken at right angles to Figure 1.

Figure 3 is a plan view of the cutting iace of the bit.

Figure 4 is a view similar to Figure 1 except that the various parts ofthe drill are shown integral, and the central cutter is ofthe reamertype.

Figure 5 is a view similar to Figure 4, except that it is at rightangles thereto, and the central cutter is illustrated as beingremovable.'

Figure 6 is a view of the cutting face of the,60

bit shown in Figures 4 and 5. l e

While in the embodiment shown in Figures 1 4k intermediate of theopposed corners 8-8 in respect to each attened portion 6 is archedupwardly as at 9 and is cut away on an incline forming the bevel surfaceI0, and this cut-away portion may be varied materially in respect to thecharacter of work being performed.

In respect to the angle of the walls of the depressionwhich form thereaming edges 5, they are illustrated as being of compound angular form,rst of all to give strength to the cutting edge and also for the purposeof lessening the amount of grinding necessary in sharpening the bit,which is always sharpened from the inside concavity by means. ofsuitable grinding wheels.

Within the hollow portion of the head I of the bit'illustrated inFigures 1 and 2 is installed the secondary 4or sub-reamer l I, itterminating downwardly in the opposed teaming edges I2 which inpractically all respects is similar to the cutting edges 5 of the outerreamer. However the lower portion of this auxiliary reamer is preferablyof cylindrical form except that it is cut-away similar to the outermostreamer, the diametrically opposite edges thereof forming the inclinedarcuate surface I3, similar to the surface I in the outer reamer, toprovide clearance for the spalls of the pilot portion of the bit. Itwill be noted that the sub-reamer is disposed with the cutting edges inalinement with the cutting edges of the outer reamer to insure freedomof the spalls so that no obstruction exists as the bit rotates duringits reciprocal action, though, obviously, in some instances, it may beequally or more eiiicient to have the medial line through each cuttingedge disposed at an angle to each other. The construction of thisauxiliary reamer differs but slightly from that of the outer reamer inthat although it is constantly forming a hole of shallow depthimmediately in advance of the work of the outer reamer, the hole is soshallow that the auxiliary reamer does not need the tapered outersurface clearance angle which is required by the larger outer reamer.This construction of the auxiliary or sub-reamer is of great.v advantagebecause it may be ground many times with the absolute minimum loss ofgage, and Provides added guidance to the drill in keeping it in perfectalinement.

'Ihe flattened sides |9- of the sub-reamer, as

well as those I8 of the central cutter portion, serve also for thepurpose of convenience relative to the unscrewing of these parts fromtheir respective sockets as by a wrench or the like.

While I have illustrated this type of bit as having a plurality ofreamers one within another and an axially disposed pilot chisel, thereamers each having two opposed arcuate cutting edges, it is to beunderstood that the reamers may be constructed with three or more sucharcuate cutting edges, as illustrated in my copending application,Serial Number 284,939, without departing from the spirit of theinvention.

In Figures 4, and 6 are illustrated certain modications of the drillbit, such, for example, as in Figure 4, wherein all cutting portions ofthe bit are shown as being of integral construction and of reamer type,as, in using a reamer, subreamer, and a reamer type cutter, it isquitepossible that the actual wear of all parts would be quite similar,and, in such a case, it is quite practical to form them in one integralpiece and sharpen the bit by means of ring grinders for the reamerportions and a cone or spherical grinder for the cutter portion.

In Figure 5 the leading cutting portion of the bit is illustrated at andis shown as being removable and attached to the head portion of the bitas by a suitable friction joint, common in the art. There are cases whenit may be desirable to use a reamer, sub-reamer, which are integrallyformed, with a cutter chisel of any ofseveral types, and thus it isillustrated as removable for such cases.

yHaving thus described my invention, what I claim and desire to secureby Letters Patent, is:

`l. A drill bit for percussion rock drilling comprising a body portionhaving an axial iiuid passageway therethrough for access of fluid to theworking face of the bit body, said body terminating at one end in acylindrical shank and means for application to the lower end of a drillrod, the body portion below said shank being hollow, enlarged anddepressed at spaced intervals about the periphery of said enlargement,

an axial depression in said body portion forming the lower outerportions of said enlargement into a plurality of spaced arcuate reamingedges.

a secondary hollow reamer of smaller diameter within the hollow of saidhead and projecting axially from said enlargement having spaceddepressions about its periphery, an axial depression within saidsecondary reamer terminatingy at its lower outer edges in a plurality ofspaced arcuate cutting edges, anda central axially disposed cutterportion within and projecting axially from and of smaller diameter thansaid sub-reamer.

2. A drill bit of the type described having an axial fluid passagewaytherethrough, comprising an outer reaming portion having a plurality ofspaced arcuate reaming edges formed by a depression therein, a secondaryreaming portion within and projecting from the depression in said outerreamer portion, said secondary reaming portion having a depressiontherein and a plurality of spaced arcuate reaming edges, and a centralcutter portion within and projecting from the depression in saidsecondary reaming portion.

3. A drill bit substantially as set forth in claim 2 wherein all of thecutting edges o! said reaming and central portions are so formed as tobreak the cuttings therefrom inwardly.

4. A drill bit substantially as set forth in claim 2 wherein the spacelbetween each pair of arcuate cutting edges is upwardly arched andbeveled to form additional cutting edges.

5. A drin bit of the type described for percussion rock drilling,comprising a substantially cylindrical shank portion, and an integralenlarged head, the lower outer portion of which terminates in aplurality of projecting arcuate reaming members and having a socketaxially within said lower -head portion, la secondary smaller reamingmember removably applied to said socket, the lower outer portion ofwhich terminates in a plurality of circumferentially spaced arcuatereaming edges projecting beyond a plane with said first mentionedreaming edges, said secondary member also having a socket axially ofandextending inwardly from` the lower outer portion thereof, and a thirdcutting member removably applied to thev socket in said secondary memberand extending beyond a .plane with the arcuate reaming edges thereof,said sockets and removable members each extending but a portion of thelength ofthe members in which they are formed to insure as sturdy anddurable a separable bit as possible.

6. A drill bit for percussion rock drilling comprising a head portionconsisting of a plurality of substantially similarly shaped reamers,progressively graduated in size, each consisting of a substantiallycylindrical body, flattened at spaced intervals about its sides andhaving an axial depression in the face and extending to the peripherythereof said depression having an axis coincident with the bit axis andforming the lower outer end into a plurality of spaced arcuate reamingcutting edges lying in the same circle, the largest of said reamersbeing removably attachable to the lower end of a string of drill rod andeach of said smaller reamers extending from the depression in the nextlarger reamer.

7. A drill bit substantially as set forth in claim 6, characterized bythe spaces intermediate of each adjacent pair of arcuate cutting edgesbeiig cut-away arcuately on an axis transverse the MARTIN HOKANSON.

